<div class="refentry" title="glPolygonOffset"><a id="glPolygonOffset"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>glPolygonOffset — set the scale and units used to calculate depth
        values</p></div><div class="refsynopsisdiv" title="C Specification"><h2>C Specification</h2><div class="funcsynopsis"><table class="funcprototype-table"><tr><td><code class="funcdef">void <b class="fsfunc">glPolygonOffset</b>(</code></td><td>GLfloat <var class="pdparam">factor</var>, </td></tr><tr><td> </td><td>GLfloat <var class="pdparam">units</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div><table class="funcprototype-table"><tr><td><code class="funcdef">void <b class="fsfunc">glPolygonOffsetx</b>(</code></td><td>GLfixed <var class="pdparam">factor</var>, </td></tr><tr><td> </td><td>GLfixed <var class="pdparam">units</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div></div></div><div class="refsect1" title="Parameters"><a id="parameters"></a><h2>Parameters</h2><div class="variablelist"><dl><dt><span class="term">
                    <em class="parameter"><code>factor</code></em>
                </span></dt><dd><p>Specifies a scale factor that is used to create a
                    variable depth offset for each polygon. The initial value
                    is 0.</p></dd><dt><span class="term">
                    <em class="parameter"><code>units</code></em>
                </span></dt><dd><p>Is multiplied by an implementation-specific value
                    to create a constant depth offset. The initial value is 0.</p></dd></dl></div></div><div class="refsect1" title="Description"><a id="description"></a><h2>Description</h2><p>When <code class="constant">GL_POLYGON_OFFSET_FILL</code>
        is enabled, each fragment's <em class="parameter"><code>depth</code></em>
        value will be offset after it is interpolated from the
        <em class="parameter"><code>depth</code></em>
        values of the appropriate vertices. The value of the offset is
        <math overflow="scroll">
            <mi>m</mi>
            <mo>*</mo>
            <mi>factor</mi>
            <mo>+</mo>
            <mi>r</mi>
            <mo>*</mo>
            <mi>units</mi>
        </math>,
        where <em class="replaceable"><code>m</code></em>
        is a measurement of the change in depth relative to the screen
        area of the polygon, and <em class="replaceable"><code>r</code></em>
        is the smallest value that is guaranteed to produce a
        resolvable offset for a given implementation. The offset is
        added before the depth test is performed and before the value
        is written into the depth buffer.</p><p>
        <code class="function">glPolygonOffset</code>
        is useful for for applying decals to surfaces.</p></div><div class="refsect1" title="See Also"><a id="seealso"></a><h2>See Also</h2><p>
        <a class="citerefentry" href="glDepthFunc"><span class="citerefentry"><span class="refentrytitle">glDepthFunc</span></span></a>,
        <a class="citerefentry" href="glEnable"><span class="citerefentry"><span class="refentrytitle">glEnable</span></span></a>
        </p></div><div class="refsect1" title="Copyright"><a id="copyright"></a><h2>Copyright</h2><p>
            Copyright © 2003-2004
            Silicon Graphics, Inc. This document is licensed under the SGI
            Free Software B License. For details, see
            <a class="ulink" href="https://web.archive.org/web/20171022161616/http://oss.sgi.com/projects/FreeB/" target="_top">https://web.archive.org/web/20171022161616/http://oss.sgi.com/projects/FreeB/</a>.
        </p></div></div>
